How the abstract modifier works in a C# class

When using the abstract modifier in C#, it indicates that the modifier has an incomplete implementation.

As well as a class, the abstract modifier can be used in properties and methods.

A class with the abstract modifier cannot be initalised directly. Instead, it needs to be inherited by a non-abstract class for it to be initalised.

Take this code:

public abstract class Currency
{
	public abstract string Symbol { get; }

	public abstract decimal USDConversationRate { get; }
}

public class USDollarsCurrency : Currency {

}

Why wouldn't this code snippet compile and what would we need to do to fix it?